The player character needs to get into the commander's office any way he or she can, which leaves four options:

Use force of attack to gain entry

Sneak

Lie to the guard and simply walk in posing as the cleaning crew

Bluff as the duty officer requires it

Afterward, head to the tanker in San Francisco. Go to the lower level of the tanker, and use it to go to the Enclave Oil Rig. Be warned, once you do use it, you cannot come back to the mainland until the game has been completed.